The present invention relates to a memory access technique that can be applied to graphic computers and entertainment devices which involve pictorial representations. More specifically, the present invention relates to a mechanism with which to allow access to a memory at high speed in terms of one of different interleaved patterns.
Typical entertainment devices constructed with a graphics computer read and execute a predetermined program and data from a recording medium, and perform image processing and sound processing according to instructions from a user. The image processing in this case can generally be classified into geometry processing and rendering processing.
The term “geometry processing” as it is generally understood in the art and used here, means the process by which coordinate transformation according to the viewpoint coordinates, perspective transformation according to the distance, clipping, and light source calculation are performed on polygons that make up an object image. With the geometry processing, farther objects appear smaller and dim. The results of the geometry processing are produced as an image display command which is also referred to as a “display list”.
The term “rendering processing” as it is generally understood in the art and used here, means the process by which the above-mentioned image display commands are interpreted to draw image data (i.e., data with pixels and Z values) to an image memory and convert the results of drawing into a predetermined signal format for display on a screen. The drawing and conversion are performed using color data assigned to each vertex of a polygon and a Z value (depth) that specifies the distance from the pixel to the plane of the eye, considering the Z values and the color of all pixels of the polygon. The image memory with the image data is updated every 1/60 seconds, for example. Thus, the object appears moving on a screen.
How fast an image is displayed to the screen depends on the access (reading/writing) speeds to the image memory, i.e., drawing speeds during the rendering operation. Images are displayed slowly at a lower drawing speed. To increase the display speeds, a memory with a large capacity which can be accessed at high speed may be used. Such memories are, however, expensive and lead to escalation of price of entertainment device products.
The present invention is made with respect to the above-mentioned circumstances. An object of the present invention is to provide an improved mechanism with which to allow access to a memory at a higher speed even without the use of a memory which can be accessed at high speed.